1. Field of the Invention
This invention relates to systems and methods for automating tracking and control of product fabrication machines. More particularly this invention relates to systems and methods for monitoring product fabrication rates and product fabrication machine efficiency.
2. Description of Related Art
Automated manufacturing systems have improved the productivity of manufacturing firms. The tool elements of a manufacturing system must be organized to produce the total product set that is marketed by the firm. To insure that the tool elements are used efficiently, a manufacturing execution system (MES) controls the operation of the tool elements and monitors the performance of the tool elements. Each tool element has actuators to activate the functions of the tool element and sensors to monitor the process of the tool element in performing its set of operations.
The MES environment provides the structure through which the structure, process, scheduling, and progress of a manufacturing process is defined, implemented, and executed. An industrial engineering or process engineering group defines the process or creates a recipe for a particular product to be fabricated. The definition is transmitted to the factory floor or process line where the process is implemented. Various tool elements are programmed to perform the various steps of the fabrication process and sensors within the tool elements are enabled to transfer status and tool element condition for monitoring the quality of the fabricated product.
The equipment engineering group is an engineering group within the manufacturing firm""s organization responsible for the design and performance of the individual tool elements. In the design and construction of the tool elements for the process line, the equipment engineering group determines or designs the tool elements to have a particular product fabrication rate capacity. Thus a measure of the performance of each tool element and the factory floor or process line is the actual rate of product fabrication. The actual rate of product fabrication is then compared with the designed or planned fabrication to determine a tool element or process line efficiency rating.
PROMIS is an MES software suite from PRI Automation, Inc. of Billerica, Mass. that provides specialty MES solutions for the semiconductor and the precision electronics industries. The solutions include process definition, version control for manufacturing operations, and monitoring and management of the tool elements of the process line or factory floor. The monitoring and management of the tool elements includes interface to the tool element automation actuators and sensors to control the function of the tool elements of each tool element. Further, the monitoring and management includes tracking progress of work-in-process as the product is fabricated. Part of the tracking includes monitoring the conditions of each tool element as the tool element performs a particular process. This includes recording the beginning and ending times of a particular process, the transport time of the work-in-process between tool elements, and recording the time of any error or alarms when a tool element malfunctions and when the malfunction is corrected and the process resumes. Further, the monitoring includes recording the duration of any time that the tool elements are idle. The idle time includes any time that a tool element is waiting for the arrival of work-in-process from preceding tool element.
International Sematech, Inc. is a consortium of semiconductor and integrated circuit manufacturing firms that have joined their resources to advance the semiconductor and integrated circuit technology. International Sematech, Inc. has promulgated a Tool Performance Tracking Platform (TP2) that provides a standard interface for gathering tool element performance information. The TP2 program automatically measures the productive time or the time a tool element is performing a manufacturing process, the idle time (standby time) or the time the tool element is waiting to begin the next process on a work-in-process, alarm duration time (interrupt time) or the time that a tool element has an error or fault condition, and the transport time or the time the work-in-process is being moved between tool elements. The Tool Performance Tracking System further allows these times to be measured by tool element, groups of tool elements, by the process or recipe, by the individual or group (lot) of the work-in-process. These time measurements allow for the monitoring of the capacity of each tool element and for all the tool elements involved in a manufacturing process. In semiconductor processing the group of tool elements will be an individual processing chamber that will process a lot of wafers (the work-in-process).
Refer now to FIG. 1 for a discussion of the method and system employed for measuring the capacity of manufacturing process or an individual tool element of the prior art. Each tool element 10 that is present on the factory floor is connected to the MES environment data base 20 to provide the necessary actuation and control to configure each tool element 10 to perform a series of processes as defined by the recipe or product plan upon a work-in-process to fabricate a particular product. In the case of a semiconductor fabrication line, the chambers receive a lot of wafers and perform the necessary process steps to form integrated circuits upon the surface of the wafers. Each sensor on the tool elements then provide the necessary condition and status information to allow monitoring of the progress of each process step and the time for the processing. Traditionally the check-in (begin of a process) or check-out (end of a process) time is manually extracted (Box 30) from the MES environment database 20. The times are collected according to a recipe and the amount of fabricated products (wafers for semiconductor processing) or lots of fabricated products processed per unit time (i.e. wafers per hour) are then calculated (Box 40). The number of fabricated products or lots of fabricated products processed is usually termed throughput. Upon completion of the calculation of the throughput 40 the MES environment database 20 is manually updated (Box 50). The throughput for each recipe is extracted from the MES environment database 20 and combined (Box 60) with the frequency of use of each recipe as planned and a capacity check system report 70 is generated.
The frequency of Box 60 is the number of performances of a given process. The capacity being the amount of production of the fabrication facility. The capacity for production of the various tool elements employed in each process is then calculated to determine the capacity for the fabrication facility. By multiplying the capability of each process and the tool element used in the process times the number of times the process is executed, any bottlenecks with in the fabrication facility can be determined. Understanding the capacity capabilities of the fabrication facility allows verification for planned future production.
The capacity of the factory floor or manufacturing process line is compared (Box 80) with the planned capacity to determine the efficiency of the factory floor or manufacturing process line. The extracting (Box 30), calculating the throughput (Box 40), and the updating (Box 50) MES environment database 20 is time consuming and manually intensive and thus cannot be performed and adjusted on a continuous basis.
U.S. Pat. No. 6,163,761 (Kent) describes a method and system for monitoring and controlling factory production. The method and system are capable of handling dynamic process production data. The electronic production system includes a memory; an input/output interface for receiving production data from a plurality of sensors detecting operation of a plurality of processes for a facility; and a processor. The processor includes a plurality of dynamically operating software modules, each responsive to the production data of a respective process for storing and dynamically updating the production data in the memory; an event log generator, responsive to the production data stored in the memory, for generating event logs and for transmitting the event logs to a management system connected to the input/output interface; and a graphic user interface, responsive to the dynamically operating software modules updating the production data, for displaying the production data graphically and dynamically as the production data changes. The electronic production system, as well as vertical integration from processes to the management system of the facility, and horizontal integration of diverse applications effect improved efficiency and inventory tracking.
U.S. Pat. No. 5,966,694 (Rothschild, et al.) illustrates a cycle time costing method and apparatus that obtains cost, efficiency, bottleneck and value creation information in a manufacturing facility. The manufacturing facility includes a plurality of production lines with each production line including a plurality of process steps. A work cell, which includes a plurality of workers or automated tool elements, is responsible for each process step. Each work cell has an associated local processing apparatus for inputting process step quantity and time information. The local processing apparatus is coupled to a central processing apparatus via local area network. The central processing apparatus then calculates cycle time costing information regarding each work cell in the manufacturing facility. The cycle time costing information may include, among other information, gross cycle time, net cycle time, bottleneck costs and scrap information for each process step and/or a product manufactured by a plurality of process steps. The cycle time cost information is then transferred to a printer or projection display nearby a work cell.
An object of this invention is to provide a method and apparatus for determining a production rate for a tool element within in a manufacturing system.
Another object of this invention is to provide a method and apparatus for determining, from the production rate, an efficiency of a tool element within a manufacturing system.
Still further another object of this invention is to provide a manufacturing execution system, which determines production rate of individual tool elements of a manufacturing process system and from the production rate of the individual tool elements, determines the production rate of the manufacturing process system.
Yet another object of this invention is to provide a manufacturing execution system, which determines from production rates of tool elements of the manufacturing process system, the efficiency of the tool elements and the efficiency of the manufacturing process system.
To accomplish at least one of these objects and other objects, a manufacturing execution system is in communication with a plurality of tool elements of a manufacturing process system. The manufacturing execution system includes a process data collection device, a data retaining device such as a memory, a time recording device, and a production rate calculator. The process data collection device is in communication with sensors located on the tool elements to receive tool element status data. The data retaining device is in communication with the process data collection device to record and retain the tool element status data. The time recording device records times of changes of the tool element status data to the data retaining device. The production rate calculator receives the records of times of changes of tool element status data and from the records of times of changes determining the product fabrication rate for the manufacturing system.
The production rate calculator is an apparatus that executes the method for determining the production rate of the individual tool elements, the production rate of the manufacturing process system, and the efficiency of the manufacturing process system. The method for determining the production rate begins by measuring the tool operation time for each tool element of the manufacturing system engaged in the manufacturing process.
The tool operation time is that time where the tool element is in operation to produce product. Therefore the measuring of the tool operation time must first determine whether the tool element is operating to produce the product. The time recording device then records the entry time. The entry time is the time at which the work-in-process enters the tool element. If a fault or malfunction of the tool element occurs an alarm event time is recorded. If the particular process for a unit of the work-in-process is complete the time recording device records an operation complete time. The production rate calculator determines the sequence of the alarm event times. A successful completion of the process of the tool element is indicated when the alarm event time occurs prior to the occurrence of the operation complete time. If the alarm event time is later than the operation complete time, the tool operation time is set as a difference between the alarm event time and the entry time. However, if the operation complete time is later than the alarm event time, the tool operation time is set as the difference between the operation time complete and the entry time.
The method then continues by next measuring an alarm duration time during fault conditions for any of the tool elements. The alarm duration time is determined by recording an alarm event time and an alarm clear time. The alarm event time is a time at which the tool element has a fault condition or malfunction and ceases operation. The alarm clear time is a time at which the tool element fault condition is corrected and the tool element able to function. The alarm duration time is determined as the difference between the alarm clear time and the alarm event time.
Next the method continues by measuring the idle duration time of each of the tool elements. The idle duration time is measured by first recording a tool element operational time. The tool element operational time is a time at which the tool element is set to be able to function. Next the alarm clear time is recorded. The alarm clear time is the time at which a tool element fault condition is corrected and the tool element able to function. Then the previous work-in-process exit time is recorded. The previous work-in-process exit time is the time at which a previous work-in-process is removed from the tool element. A next work-in-process entry time is then recorded. The next work-in-process entry time is the time at which the next work-in-process enters the tool element. The idle duration time is then determined as the difference between the next work-in-process entry time and a latest time of the tool element operational time, the alarm clear time, and the previous work-in-process exit time.
The method further measures a product transport time. The product transport time indicates an amount of time that a work-in-process is being transported between tool elements. The measuring the product transport time begins by recording the exit time at which the work-in-process is removed from a previous tool element (ROBOT ARM START) and recording the entry time at which the work-in-process is placed in a next tool element (ROBOT ARM COMPLETE). The transport time is determined as the difference between the exit time and the entry time.
All the tool operation times terminated with an alarm event time are discarded. The remaining tool operation times are then averaged to create an average tool operation time and the standard deviation of all tool operation times is found. All tool operation times greater than and less than a sum and difference of the average tool operation time and a multiplication factor of the standard deviation (i.e. 3 standard deviations). All tool operation times not discarded are then summed with the product transport times, and the idle duration times. The number of products fabricated is then divided by the summed tool operation times, product transport times, and the idle duration times.
The fabricated products are grouped in fabrication lots and the tool operation time indicates a time to fabricate one lot of fabricated product and the transport time is the time to transport the fabrication lot. The unit transport time must then be calculated from the number of units of fabricated products per lot.
The efficiency of the manufacturing system is determined by the manufacturing execution system by acquiring a planned manufacturing system production rate from an engineering planning system in communication with the manufacturing execution system. The production rate calculator then calculates the production efficiency factor by comparing the planned manufacturing system production rate as a percentage of the determined product fabrication rate.